The present invention relates generally to voltage regulators, and more particularly to control systems for switching voltage regulators.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones. Switching voltage regulators (or more simply "switching regulators") are known to be an efficient type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency voltage to generate the output DC voltage. Typically, the switching regulator includes a switch for alternately coupling and de-coupling an input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, is coupled between the input voltage source and the load to filter the output of the switch and thus provide the output DC voltage. A controller measures an electrical characteristic of the circuit, e.g., the voltage or current passing through the load, and sets the duty cycle of the switch in order to maintain the output DC voltage at a substantially uniform level.
Voltage regulators for microprocessors are subject to ever more stringent performance requirements. One trend is to operate at higher currents, e.g., 35-50 amps. Another trend is to turn on or off different parts of the microprocessor in each cycle in order to conserve power. This requires that the voltage regulator react very quickly to changes in the load, e.g., several nanoseconds to shift from the minimum to the maximum load. Another trend is to require the voltage regulator to have a "standby mode" which consumes little power at low loads. In addition to these specific trends, high efficiency is generally desirable in order to avoid thermal overload at high loads and to increase battery life in portable systems.
Unfortunately, some conventional voltage regulators operate well at either large or small loads, but not both. In addition, some buck regulators do not function properly when the output voltage is comparable to the input voltage. Other problems that occur in voltage regulators include the following: large ripple current losses, voltage overshooting during start-up and quickly changing load conditions, and electrical noise from the opening and closing of the power switches in the regulator.
Conventional controllers often employ analog control and design techniques to achieve voltage regulation. Such techniques often result in implementations of comparatively large die area and design complexity. Moreover, such implementations are not easily integrated into larger systems or ported among different processing technologies.
In view of the foregoing, there is room for improvement in voltage regulators and control systems for voltage regulators.